Injection locked on-chip laser to external on-chip resonator

ABSTRACT

Various technologies described herein pertain to injection locking on-chip laser(s) and external on-chip resonator(s). A system includes a first integrated circuit chip and a second integrated circuit chip. The first integrated circuit chip and the second integrated circuit chip are separate integrated circuit chips and can be optically coupled to each other. The first integrated circuit chip includes a laser configured to emit light via a first path and a second path. The second integrated circuit chip includes a resonator formed of an electrooptic material. The resonator can receive the light emitted by the laser of the first integrated circuit chip via the first path and return feedback light to the laser of the first integrated circuit chip via the first path. The feedback light can cause injection locking of the laser to the resonator to control the light emitted by the laser (e.g., via the first and second paths).

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/836,302, filed on Mar. 31, 2020, and entitled “INJECTION LOCKEDON-CHIP LASER TO EXTERNAL ON-CHIP RESONATOR”, the entirety of which isincorporated herein by reference.

BACKGROUND

Various conventional architectures employ a laser that is injectionlocked to a resonator. For instance, the laser can emit light that issent to the resonator. The laser and the resonator are opticallycoupled, such that the light from the laser is provided to theresonator, circulates inside the resonator undergoing total internalreflection, and is provided back from the resonator to the laser. Whenself-injection locked, the frequency of the laser is a slave to thefrequency of the resonator (e.g., the resonator can cause the laser toemit light at substantially similar frequency as compared to thefrequency of the resonator) and a linewidth of the light emitted by thelaser can be reduced as compared to a laser that is not injectionlocked.

A frequency modulated continuous wave (FMCW) laser source can include alaser that is injection locked to a resonator. For instance, an FMCWlaser source can be utilized as part of an FMCW lidar sensor system.Such FMCW lidar sensor system can be used for perception of range andvelocity of a moving target. By way of illustration, an autonomousvehicle can include an FMCW lidar sensor system; the FMCW lidar sensorsystem of the autonomous vehicle can capture data pertaining to rangeand velocity of object(s) within a driving environment nearby theautonomous vehicle. Accordingly, it is desirable to narrow a linewidthof light emitted by an FMCW laser source while reducing size and weightof such laser source.

Some conventional resonators that can be utilized for injection lockingare discrete components that can be in optical communication with thelaser. Due to electrooptic properties and sizes of such resonators,frequency of light circulating in a resonator can be linearly modulated.According to an example, voltage in a sawtooth waveform can be appliedto the resonator to cause the laser injection locked to the resonator toemit a light beam with a frequency that follows the sawtooth waveform(e.g., an optical chirp). However, conventional discrete resonators maybe difficult to manufacture and may be relatively large in size.Further, conventional discrete resonators, due to typical sizes, maysupport a plurality of modes. Since such resonators can support a numberof higher order modes, it is often difficult to injection lock the laserto the fundamental mode of the resonators.

Moreover, various conventional laser architectures include twointegrated circuit chips that are coupled to each other. For example, insome traditional chip-to-chip coupled architectures, a first integratedcircuit chip includes a laser and a second integrated circuit chipincludes various optical components; however, in these architectures,light is outputted by the second integrated circuit chip (e.g., thesecond integrated circuit chip does not provide feedback to the firstintegrated circuit chip). Following this example, the laser is notinjection locked to component(s) of the second integrated circuit chip.According to other examples where chip-to-chip coupling is employed, afirst integrated circuit chip formed of a broadband gain material with afirst mirror can be coupled to a second integrated circuit chip, wherethe second integrated circuit chip includes a second mirror; thus, thefirst integrated circuit chip and the second integrated circuit chip incombination forms a laser. However, by itself, the broadband gainmaterial with the first mirror of the first integrated circuit chip isnot a laser source. The gain material that is part of the firstintegrated circuit chip cannot function as a laser source until coupledwith the second mirror of the second integrated circuit chip. Followingthis example, a hybrid laser is provided across the two integratedcircuit chips. Accordingly, the foregoing conventional chip-to-chipcoupled architectures may rely on linearly ramping laser current tocreate optical chirps for an FMCW lidar sensor system.

SUMMARY

The following is a brief summary of subject matter that is described ingreater detail herein. This summary is not intended to be limiting as tothe scope of the claims.

Described herein are various technologies that pertain to injectionlocking an on-chip laser and an external on-chip resonator. According tovarious embodiments, a system can include a first integrated circuitchip and a second integrated circuit chip. The first integrated circuitchip and the second integrated circuit chip are separate integratedcircuit chips. The first integrated circuit chip can be opticallycoupled with the second integrated circuit chip. The first integratedcircuit chip includes a laser configured to emit light via a first pathand a second path (e.g., the first path and the second path can be afirst waveguide and a second waveguide). The second integrated circuitchip includes a resonator formed of an electrooptic material. Theresonator can be configured to receive the light emitted by the laser ofthe first integrated circuit chip via the first path and return feedbacklight to the laser of the first integrated circuit chip via the firstpath. The feedback light can cause injection locking of the laser to theresonator to control the light emitted by the laser (e.g., via the firstpath and the second path). Controlling the light emitted by the laserincludes controlling one or more spectral properties of the lightemitted by the laser.

According to various embodiments, the first integrated circuit chip canfurther include a lidar optical engine. The lidar optical engine caninclude one or more lidar components. Examples of the lidar componentsinclude a splitter, an optical amplifier, an output, a return, aninterferometer, a balanced detector, and the like. The light emitted bythe laser via the second path can be inputted to the lidar opticalengine. However, it is contemplated that the first integrated circuitchip can include other components if the light being emitted by thelaser is used for an application other than lidar.

In accordance with various embodiments, the resonator of the secondintegrated circuit chip can be optically coupled to the laser of thefirst integrated circuit chip, where the resonator has an add/dropresonator configuration. The second integrated circuit chip can furtherinclude a mirror and a waveguide, where an end of the waveguide isconfigured to be optically coupled to the first integrated circuit chip.The mirror can be, for example, a loop mirror, a Bragg mirror, or afacet mirror. The mirror can provide additional feedback to the laser toenhance efficiency of the injection lock. In the add/drop resonatorconfiguration, the resonator can include a first coupling regionevanescently coupled to the waveguide, and a second coupling regionevanescently coupled to the mirror.

Moreover, pursuant to various embodiments, the first integrated circuitchip can include a plurality of lasers and the second integrated circuitchip can include a plurality of resonators. More particularly, the firstintegrated circuit chip can include at least a first laser and a secondlaser. Further, the second integrated circuit chip can include at leasta first resonator and a second resonator. The first resonator and thesecond resonator can be formed of an electrooptic material. The firstresonator can be configured to receive light emitted by the first laserof the first integrated circuit chip and return feedback light to thefirst laser of the first integrated circuit chip. The feedback lightreturned by the first resonator can cause injection locking of the firstlaser to the first resonator to control light emitted by the firstlaser. Moreover, the second resonator can be configured to receive lightemitted by the second laser of the first integrated circuit chip andreturn feedback light to the second laser of the first integratedcircuit chip. The feedback light returned by the second resonator cancause injection locking of the second laser to the second resonator tocontrol the light emitted by the second laser. The first integratedcircuit chip can further include a plurality of lidar optical engines.For instance, the first integrated circuit chip can include at least afirst lidar optical engine and a second lidar optical engine.Accordingly, the light emitted by the first laser can be inputted to thefirst lidar optical engine and the light emitted by the second laser canbe inputted to the second lidar optical engine. Thus, pursuant to suchembodiments, the first integrated circuit chip and the second integratedcircuit chip can provide multiple channels.

Further, according to various embodiments, the second integrated circuitchip can include a resonator that can be optically coupled to more thanone laser of the first integrated circuit chip. Accordingly, theresonator can be configured to receive light emitted by a first laser ofthe first integrated circuit chip and return feedback light to the firstlaser of the first integrated circuit chip, where the feedback lightreturned by the resonator can cause injection locking of the first laserto the resonator to control light emitted by the first laser. Moreover,the resonator can also be configured to receive light emitted by asecond laser of the first integrated circuit chip, where the feedbacklight returned by the resonator can cause injection locking of thesecond laser to the resonator to control the light emitted by the secondlaser.

The above summary presents a simplified summary in order to provide abasic understanding of some aspects of the systems and/or methodsdiscussed herein. This summary is not an extensive overview of thesystems and/or methods discussed herein. It is not intended to identifykey/critical elements or to delineate the scope of such systems and/ormethods. Its sole purpose is to present some concepts in a simplifiedform as a prelude to the more detailed description that is presentedlater.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary system configured to injection lock alaser to a resonator, where a first integrated circuit chip includes thelaser and a second integrated circuit chip includes the resonator.

FIGS. 2-5 illustrate exemplary embodiments of the system that includesthe first integrated circuit chip and the second integrated circuit chipof FIG. 1 .

FIG. 6 illustrates an exemplary system for multiple channel, on-chipresonator to laser coupling.

FIGS. 7-8 illustrate exemplary embodiments of the system for multiplechannel, on-chip resonator to laser coupling of FIG. 6 .

FIG. 9 illustrates a block diagram of an exemplary lidar sensor systemthat includes a laser injection locked to a resonator as describedherein.

FIG. 10 is a flow diagram that illustrates an exemplary methodology ofinjection locking a laser to a resonator.

DETAILED DESCRIPTION

Various technologies pertaining to on-chip laser(s) injection locked toexternal on-chip resonator(s) are now described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of one or more aspects. It may be evident,however, that such aspect(s) may be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form in order to facilitate describing one or moreaspects. Further, it is to be understood that functionality that isdescribed as being carried out by certain system components may beperformed by multiple components. Similarly, for instance, a componentmay be configured to perform functionality that is described as beingcarried out by multiple components.

Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase “X employs A or B” is intended to mean anyof the natural inclusive permutations. That is, the phrase “X employs Aor B” is satisfied by any of the following instances: X employs A; Xemploys B; or X employs both A and B. In addition, the articles “a” and“an” as used in this application and the appended claims shouldgenerally be construed to mean “one or more” unless specified otherwiseor clear from the context to be directed to a singular form.

As used herein, the terms “component” and “system” are intended toencompass computer-readable data storage that is configured withcomputer-executable instructions that cause certain functionality to beperformed when executed by a processor. The computer-executableinstructions may include a routine, a function, or the like. The terms“component” and “system” are also intended to encompass one or moreoptical elements that can be configured or coupled together to performvarious functionality with respect to an optical signal. It is also tobe understood that a component or system may be localized on a singledevice or distributed across several devices. Further, as used herein,the term “exemplary” is intended to mean “serving as an illustration orexample of something.”

As described herein, one aspect of the present technology is thegathering and use of data available from various sources to improvequality and experience. The present disclosure contemplates that in someinstances, this gathered data may include personal information. Thepresent disclosure contemplates that the entities involved with suchpersonal information respect and value privacy policies and practices.

As used herein, and unless the context dictates otherwise, the term“coupled to” is intended to include both direct coupling (in which twoelements that are coupled to each other contact each other) and indirectcoupling (in which at least one additional element is located betweenthe two elements).

Referring now to the drawings, FIG. 1 illustrates an exemplary system100 configured to injection lock a laser 102 to a resonator 104. Thesystem 100 includes a first integrated circuit chip 106 and a secondintegrated circuit chip 108. The first integrated circuit chip 106 andthe second integrated circuit chip 108 are separate integrated circuitchips. Moreover, the first integrated circuit chip 106 and the secondintegrated circuit chip 108 can be optically coupled with each other.The first integrated circuit chip 106 includes the laser 102. Further,the second integrated circuit chip 108 includes the resonator 104.

The laser 102 can be heterogeneously integrated on the first integratedcircuit chip 106. The laser 102 of the first integrated circuit chip 106is configured to emit light in two directions. Thus, the laser 102 canemit light via a first path 110 and a second path 112. The first path110, for instance, can include a first waveguide of the first integratedcircuit chip 106 and the second path 112 can include a second waveguideof the first integrated circuit chip 106. The laser 102 can be asemiconductor laser, for instance. According to various examples, thelaser 102 can be a distributed feedback (DFB) laser, a distributed Braggreflector (DBR) laser, a Fabry Perot laser, or the like.

The resonator 104 is configured to receive the light emitted by thelaser 102 of the first integrated circuit chip 106 via the first path110 and return feedback light to the laser 102 of the first integratedcircuit chip 106 via the first path 110. The light received by theresonator 104 can circulate inside the resonator 104 undergoing totalinternal reflection. The feedback light can cause injection locking ofthe laser 102 to the resonator 104 to control the light emitted by thelaser 102; thus, the feedback light from the resonator 104 can controlthe light emitted by the laser 102 via the first path 110 and the secondpath 112. Controlling the light emitted by the laser 102 includescontrolling one or more spectral properties of the light emitted by thelaser 102. Changing the one or more spectral properties of the lightemitted by the laser 102 via injection locking can produce a narrowlinewidth, low noise laser source.

The resonator 104 is formed of an electrooptic material. Examples of theelectrooptic material from which the resonator 104 can be formed includelithium niobate and lithium tantalate. For instance, the resonator 104can be fabricated from a lithium niobate on insulator (LNOI) platform.Other examples of the electrooptic material from which the resonator 104can be formed include materials that are oftentimes dielectric but areprocessed to cause such materials to be electrooptic; for instance,strained silicon (where strain on the silicon provides an electroopticeffect) can be used as the electrooptic material from which theresonator 104 can be formed. According to an illustration, a substrateof the second integrated circuit chip 108 can be formed of silicon, anoxide buffer layer can be formed above the substrate, and theelectrooptic material from which the resonator 104 is formed can bebonded above the oxide buffer layer; yet, the claimed subject matter isnot so limited.

The laser 102 is optically injection locked to the resonator 104. Sincethe laser 102 is optically injection locked to the resonator 104, avoltage applied across the resonator 104 can impart a frequency changeon the laser 102 as well as a linewidth reduction. Injection locking ofthe laser 102 to the resonator 104 can narrow a linewidth of lightemitted by the laser 102. Accordingly, the voltage applied to theresonator 104 can be utilized to control frequency of the injectionlocked light outputted by the laser 102. The injection locked light(e.g., the emitted light), for instance, can be or include an opticalchirp for a lidar sensor system generated by applying a voltage waveformacross the resonator 104.

Moreover, the second integrated circuit chip 108 can include a mirror114 optically coupled to the resonator 104. The mirror 114 can be a loopmirror, a Bragg mirror, a facet mirror, or the like. The mirror 114 canprovide additional feedback to the laser 102. For instance, the mirror114 can act as a filter, which can reflect light that can be coupledback to the resonator 104 (and further provided back to the laser 102).Such additional feedback can increase an efficiency of the injectionlocking of the laser 102 to the resonator 104. The mirror 114 can betunable, for example; following this example, the mirror 114 can includeelectrodes that can be used to control an amount of light that isreturned by the mirror 114.

As described in greater detail herein, the second integrated circuitchip 108 can further include electrode(s) adjacent to the resonator 104;accordingly, a voltage can be applied to such electrode(s). Applicationof a voltage to the electrode(s) across the resonator 104 can change anoptical property of the electrooptic material of the resonator 104. Forinstance, application of a voltage across the resonator 104 can changean index of refraction of the electrooptic material of the resonator104.

The on-chip laser 102 can be coupled with the high quality factor (Q)external resonator 104 (e.g., external cavity) through chip-to-chipcoupling of the first integrated circuit chip 106 and the secondintegrated circuit chip 108. Self-injection locking of the laser 102 tothe resonator 104 can provide a low-noise, narrow linewidth lightsource. Thus, the system 100 can provide an injection locking mechanismthat can reduce linewidth of the light outputted by the laser 102, whichcan increase a coherence range of the system 100 (e.g., a lidar sensorsystem that includes the system 100).

When self-injection locked, a frequency of emitted light from the laser102 can coincide with a frequency of a waveguide mode (WGM) of theresonator 104. Since the resonator material is electrooptic, the voltageapplied across the resonator 104 can be utilized to change the frequencyof the waveguide mode, and thus, can modulate the frequency of the lightoutputted by the laser 102. Accordingly, the system 100 can be utilizedto provide a frequency modulated continuous wave (FMCW) laser source.The FMCW laser source can be controlled by applying an electric field tothe resonator 104 at different rates or in varying patterns. The FMCWlaser source can have high spectral purity. Thus, the system 100 (e.g.,the FMCW laser source) can be utilized for various applications such aslidar, optical metrology, high bitrate optical communication,high-resolution optical sensing, optical coherence tomography (OCT),other biomedical sensors, or the like. For example, a lidar sensorsystem (e.g., of an autonomous vehicle) can include the system 100.Following this example, the laser 102 injection locked to the resonator104 can be an FMCW laser source configured to generate an optical chirp(e.g., the injection locked light) for the lidar sensor system; yet, itis also contemplated that the system 100 can also be used as part ofother systems that use compact, narrow linewidth lasers.

The system 100 can provide an FMCW laser source that can be used forperception of range and velocity of a moving target. Accordingly, thesystem 100 can provide an integrated, low noise, narrow linewidth,frequency modulated laser source on the first integrated circuit chip106 and the second integrated circuit chip 108. For instance, use of thesystem 100 as part of a lidar sensor system can lead to reduction incosts, size, weight, and/or power consumption of the lidar sensor systemrelative to conventional lidar sensor systems. Moreover, the on-chiplaser 102 can be stabilized by self-injection locking to the on-chipextended cavity (e.g., the resonator 104). The extended cavity can be ahigh Q resonator 104 fabricated out of electrooptic material and canhave electrodes for frequency modulation. Moreover, in addition tolinewidth narrowing and stabilization, the scalable on-chip extendedcavity can reduce size and weight of the FMCW laser by orders ofmagnitude as well as can reduce manufacturing costs by enablinglarge-scale manufacturing.

Accordingly, the system 100 can be (or be included in) an on-chip FMCWlaser source. Moreover, an FMCW laser source that includes the system100 can have a reduced size or weight relative to conventional lasersources. Further, power consumption can be reduced utilizing the FMCWlaser source that includes the system 100 relative to conventionalapproaches. As described in greater detail below, it is alsocontemplated that the techniques set forth herein can be scalable formulti-channel output.

Now turning to FIG. 2 , illustrated is an exemplary embodiment of thesystem 100 that includes the first integrated circuit chip 106 and thesecond integrated circuit chip 108. Again, the first integrated circuitchip 106 includes the laser 102, and the second integrated circuit chip108 includes the resonator 104 and the mirror 114. The laser 102 isconfigured to emit light via a first path and a second path; as depictedin FIG. 2 , the laser 102 is configured to emit light in a firstdirection via a first waveguide 202 and in a second direction via asecond waveguide 204. The light emitted by the laser 102 in the firstdirection via the first waveguide 202 can be sent to the resonator 104.More particularly, the waveguide 202 can end with a facet or edgecoupler that can be butt coupled to the second integrated circuit chip108 that stages the external cavity (e.g., the resonator 104).

The first integrated circuit chip 106 can further include a lidaroptical engine 206. The lidar optical engine 206 can include one or morelidar components. For instance, the lidar optical engine 206 can includelidar components such as a splitter, an optical amplifier, an output, areturn, an interferometer, a balanced detector, a combination thereof,and so forth on the same platform as the laser 102 (e.g., on the firstintegrated circuit chip 106). The light emitted by the laser 102 in thesecond direction via the second waveguide 204 (e.g., injection locked tothe resonator 104) can be inputted to the lidar optical engine 206;thus, the injection locked light from the laser 102 can be inputted tothe lidar optical engine 206 via the second path. While many of theexamples described herein provide the first integrated circuit chip 106including lidar optical engine(s), is to be appreciated that other typesof components can additionally or alternatively be included as part ofthe first integrated circuit chip 106 depending on the application forwhich the system 100 is being utilized.

The resonator 104 of the second integrated circuit chip 108 can be asingle mode optical resonator. In contrast, in some conventionalapproaches, a resonator injection locked to a laser includes one or morehigher order modes. Since the resonator 104 of the second integratedcircuit chip 108 can be a single mode optical resonator, such resonator104 supports injection locking to the fundamental mode a priori.

Moreover, the resonator 104 can be or include a closed-loop waveguide.The closed-loop waveguide, for instance, can include bent sectionsand/or straight sections. The dimensions of the sections of theclosed-loop waveguide can be set such that the resonator 104 supports asingle optical mode. A width of the waveguide forming the resonator 104(denoted w in FIG. 2 , also referred to as the width of the resonator104), for instance, can be in a range from 1 micron to 3 microns. Due tothe width of the resonator 104, a stronger field can result across thewidth of the resonator 104 as compared to conventional, largerresonators (assuming the same voltage is applied across the resonators).However, the claimed subject matter is not so limited as other widths ofthe resonator 104 are intended to fall within the scope of the heretoappended claims.

The second integrated circuit chip 108 further includes electrodes208-210 adjacent to the resonator 104. The electrodes 208-210 and theresonator 104 can be located in a common plane (above a top surface of asubstrate of the second integrated circuit chip 108). According to anexample, the electrodes 208-210 can be directly coupled to the resonator104 (e.g., the electrodes 208-210 can be on the waveguide without spaceor other material between the electrodes 208-210 and the resonator 104).Pursuant to another example, the electrodes 208-210 can be indirectlycoupled to the resonator 104 (e.g., space and/or other material can bepositioned between at least one of the electrodes 208-210 and theresonator 104). Since the electrodes 208-210 are adjacent to theresonator 104, a change in voltage applied across the electrodes 208-210can cause a corresponding change in frequency of a waveguide mode of theresonator 104.

It is to be appreciated that the electrodes 208-210 can be substantiallyany length (denoted 1 in FIG. 2 ). For instance, longer electrodes208-210 can allow for more effectively controlling the change in indexof refraction of the resonator 104.

While the electrodes 208-210 shown in FIG. 2 are illustrated as being ina common plane with the resonator 104 relative to a top surface of asubstrate of the second integrated circuit chip 108, in otherembodiments it is to be appreciated that the electrodes 208-210 can bevertically stacked with the resonator 104. For instance, a firstelectrode can be beneath the resonator 104 and a second electrode can beabove the resonator 104 relative to the top surface of the substrate ofthe second integrated circuit chip 108.

The resonator 104 can be coupled to the laser 102, where the resonator104 has an add/drop resonator configuration. The second integratedcircuit chip 108 can further include a waveguide 212 as well as themirror 114. An end of the waveguide 212 is configured to be opticallycoupled to the first integrated circuit chip 106 (e.g., a facet or edgecoupler can be at the end of the waveguide 212). More particularly, theend of the waveguide 212 is configured to be optically coupled to theend of the waveguide 202 of the first integrated circuit chip 106 (e.g.,the waveguide 212 and the waveguide 202 are to be aligned such thatlight can propagate there between). Moreover, the resonator 104 (havingthe add/drop resonator configuration) includes a first coupling region214 evanescently coupled to the waveguide 212 and a second couplingregion 216 evanescently coupled to the mirror 114. The first couplingregion 214 and the second coupling region 216 can be designed to providedesired coupling strengths between the resonator 104 and the waveguide212 as well as between the resonator 104 and the mirror 114. Thus, anadd port of the resonator 104 (e.g., the first coupling region 214) canend on a facet to be coupled with the first integrated circuit chip 106(e.g., the end of the waveguide 212). Further, an output of the dropport of the resonator 104 (e.g., the second coupling region 216) caninclude the mirror 114 (e.g., a loop mirror, a Bragg mirror, a facetmirror, or the like). As noted above, the mirror 114 can provideadditional feedback to the laser 102 to increase the efficiency of theinjection lock.

A detector (e.g., photodiode) (not shown) can be coupled to thewaveguide 212. The detector can allow for detecting whether the firstintegrated circuit chip 106 and the second integrated circuit chip 108are aligned.

Further, the second integrated circuit chip 108 can include electrodes218-220 adjacent to the waveguide 212. Similar to the electrodes208-210, the electrodes 218-220 can be directly coupled or indirectlycoupled to the waveguide 212. Moreover, the electrodes 218-220 and thewaveguide 212 can be in a common plane relative to the top surface ofthe substrate of the second integrated circuit chip 108; yet, it is alsocontemplated that the electrodes 218-220 and the waveguide 212 canalternatively be vertically stacked relative to the top surface of thesubstrate of the second integrated circuit chip 108. A change in voltageapplied across the electrodes 218-220 can cause a corresponding phaseshift of the feedback light returned to the laser 102 of the firstintegrated circuit chip 106. The change in voltage applied across theelectrodes 218-220 can change a refractive index of the waveguide 212,which can change a delay of light traveling through a section of thewaveguide 212. Thus, by adding the electrodes 218-220, the add port maybe coupled to a phase shifter to facilitate injection locking.

The laser 102 on the first integrated circuit chip 106 is injectionlocked to the extended cavity (e.g., the resonator 104) on the secondintegrated circuit chip 108, which provides feedback light to the laser102. As described herein, self-injection locking of the laser 102 to thehigh Q cavity (e.g., the resonator 104) can reduce laser linewidth andnoise by orders of magnitude as compared to various conventionalapproaches. Chip-to-chip alignment is used to enable such feedbackbetween the resonator 104 and the laser 102 (e.g., the waveguide 212 ofthe second integrated circuit chip 108 is to be aligned with thewaveguide 202 of the first integrated circuit chip 106). Moreover,anti-reflection coatings and index matching epoxy can be utilized tomitigate chip facet reflection and mitigate loss. While being shown asseparated in FIG. 2 , it is to be appreciated that the first integratedcircuit chip 106 and the second integrated circuit chip 108 can bedirectly connected to each other.

Now turning to FIG. 3 , illustrated is another exemplary embodiment ofthe system 100 including the first integrated circuit chip 106 and thesecond integrated circuit chip 108. Similar to above, the firstintegrated circuit chip 106 can include the laser 102, the waveguides202-204, and the lidar optical engine 206. Moreover, the secondintegrated circuit chip 108 can include the resonator 104, the mirror114, the waveguide 212, the electrodes 208-210 adjacent to the resonator104, and the electrodes 218-220 adjacent to the waveguide 212.

In addition to the electrodes 208-210 adjacent to the resonator 104, thesecond integrated circuit chip 108 can also include another set ofelectrodes 302-304 adjacent to the resonator 104. Similar to theelectrodes 208-210, the electrodes 302-304 can be directly or indirectlycoupled to the resonator 104. Moreover, as depicted in FIG. 3 , theresonator 104, the electrodes 208-210, and the electrodes 302-304 can bein a common plane relative to the top surface of the substrate of thesecond integrated circuit chip 108.

According to various embodiments, the electrode 208 and the electrode302 can be electrically connected on the second integrated circuit chip108. Moreover, the electrode 210 and the electrode 304 can beelectrically connected on the second integrated circuit chip 108. Forinstance, the electrode 208 and the electrode 302 can be connected toV+, and the electrode 210 and the electrode 304 to be connected toground; however, the claimed subject matter is not so limited. Byincluding the second set of electrodes 302-304 in the second integratedcircuit chip 108, an electric field across the resonator 104 can beincreased relative to the configuration depicted in FIG. 2 .

Now turning to FIG. 4 , illustrated is yet another exemplary embodimentof the system 100 including the first integrated circuit chip 106 andthe second integrated circuit chip 108. Similar to above, the firstintegrated circuit chip 106 can include the laser 102, the waveguides202-204, and the lidar optical engine 206. Moreover, the secondintegrated circuit chip 108 can include the resonator 104, the mirror114, the waveguide 212, and the electrodes 208-210 adjacent to theresonator 104. Although not shown, it is contemplated that the secondintegrated circuit chip 108 can further include a second set ofelectrodes (e.g., the electrodes 302-304) adjacent to the resonator 104.

As depicted in FIG. 4 , the first integrated circuit chip 106 caninclude electrodes 402-404 adjacent to the waveguide 202. Similar to theelectrodes 218-220 adjacent to the waveguide 212 described above, theelectrodes 402-404 can be directly or indirectly coupled to thewaveguide 202. Likewise, similar to the electrodes 218-220, theelectrodes 402-404 can be utilized to control a phase shift of feedbacklight returned to the laser 102 of the first integrated circuit chip106. According to an example, a change in voltage applied across theelectrodes 402-404 can change a refractive index of the waveguide 202,which can change a delay of light traveling through a section of thewaveguide 202. However, pursuant to other examples, the electrodes402-404 can be connected to an integrated diode that can inject carriersto induce a refractive index shift or the electrodes 402-404 can beattached to a resistive heater that can dissipate heat to induce arefractive index shift.

Moreover, according to various embodiments, it is to be appreciated thatthe system 100 can include both sets of phase shift electrodes. Thus, inaccordance with such embodiments, the first integrated circuit chip 106can include the electrodes 402-404 adjacent to the waveguide 202, andthe second integrated circuit chip 108 can include the electrodes218-220 adjacent to the waveguide 212.

Now turning to FIG. 5 , illustrated is another exemplary embodiment ofthe system 100 that includes the first integrated circuit chip 106optically coupled to the second integrated circuit chip 108. Moreparticularly, FIG. 5 shows the lidar optical engine 206 of the firstintegrated circuit 106 in greater detail. Similar to above, the laser102 of the first integrated circuit chip 106 is injection locked to theresonator 104 of the second integrated circuit chip 106. Moreover,injection locked light emitted by the laser 102 is inputted to the lidaroptical engine 206.

The lidar optical engine 206 can include a splitter 502, an output 504,a return 506, an interferometer 508, and a balanced detector 510.Moreover, although not shown, is to be appreciated that the lidaroptical engine 206 can include other components (e.g., an opticalamplifier, etc.). The splitter 502 can receive the light emitted by thelaser 102 and split such light beam into an output light beam (e.g., tobe transmitted into an environment via the output 504) and a localoscillator signal. A returned light beam received from the environmentresponsive to transmission of the output light beam (e.g., due to theoutput light beam being reflected by an object in the environment) canbe received via the return 506. The returned light beam and the localoscillator signal can be merged by the interferometer 508, and outputfrom the interferometer 508 can be provided to the balanced detector510.

Now turning to FIG. 6 , illustrated is a system 600 for multiplechannel, on-chip resonator to laser coupling. The system 600 includes afirst integrated circuit chip 602 and a second integrated circuit chip604. The first integrated circuit chip 602 and the second integratedcircuit chip 604 are separate integrated circuit chips, which can beoptically coupled to each other. The first integrated circuit chip 602includes a plurality of lasers (e.g., an array of lasers), namely, alaser 606, . . . , and a laser 608. It is to be appreciated that thefirst integrated circuit chip 602 can include substantially any numberof lasers 606-608. Further, the lasers 606-608 can each be substantiallysimilar to the laser 102 described herein. Moreover, the secondintegrated circuit chip 604 includes a plurality of resonators (e.g., anarray of resonators), namely, a resonator 610, . . . , and a resonator612. The number of resonators 610-612 on the second integrated circuitchip 604 can equal the number of lasers 606-608 on the first integratedcircuit chip 602. Further, the resonators 610-612 can each besubstantially similar to the resonator 104 described herein. Theresonators 610-612 can each be optically coupled to a correspondingmirror 614-616 (each substantially similar to the mirror 114 describedherein).

The first integrated circuit chip 602 and the second integrated circuitchip 604 include multiple channels. For instance, a first channel caninclude the laser 606, the resonator 610, and the mirror 614. Further, asecond channel can include the laser 608, the resonator 612, and themirror 616. Each of the channels can be substantially similar to thechannel of the first integrated circuit chip 106 and the secondintegrated circuit chip 108 described above in FIGS. 1-5 ; accordingly,the foregoing description of the single channel can be extended to themultiple channel embodiments described herein.

As described herein, the resonators 610-612 are formed of electroopticmaterial. The resonators 610-612 can be spaced on the second integratedcircuit chip 604 at a defined pitch to couple to a same number of lasers606-608 on the first integrated circuit chip 602 for injection lockingto obtain multiple narrow linewidth, low phase noise, on-chip sources inthe system 600. Accordingly, the resonator 610 is configured to receivelight emitted by the laser 606 of the first integrated circuit chip 602and return feedback light to the laser 606 of the first integratedcircuit chip 602. The feedback light returned by the resonator 610 cancause injection locking of the laser 606 to the resonator 610 to controlthe light emitted by the laser 606. Likewise, the resonator 612 can beconfigured to receive light emitted by the laser 608 of the firstintegrated circuit chip 602 and return feedback light to the laser 608of the first integrated circuit chip 602. The feedback light returned bythe resonator 612 can cause injection locking of the laser 608 to theresonator 612 to control the light emitted by the laser 608. It is to beappreciated that other resonators of the second integrated circuit chip604 (if the system 600 includes more than two channels) can similarly beoptically coupled to other lasers of the first integrated circuit chip602.

The first integrated circuit chip 602 can include the same number oflasers 606-608 as there are resonators 610-612 on the second integratedcircuit chip 604. As described herein, the lasers 606-608 can each emitlight in two directions. As described herein, outputs from the lasers606-608 in a first direction (e.g., along a first path, via a firstwaveguide) can come to an edge of the first integrated circuit chip 602with the same spacing as outputs from the resonators 610-612 of thesecond integrated circuit chip 604.

The second integrated circuit chip 604 can include an array of highquality factor resonators 610-612. The resonators 610-612 may be coupledin an add/drop resonator configuration, and outputs of the drop portsmay be coupled to corresponding mirrors 614-616 (e.g., loop mirrors,Bragg mirrors, facet mirrors, or the like). Moreover, the secondintegrated circuit chip 604 can include electrodes adjacent to theresonators 610-612 to allow for applying fields across the resonator610-612 for chirping in order to achieve frequency modulation. It iscontemplated that the second integrated circuit chip 604 can include 2,4, 8, or N resonators 610-612, where N can be substantially any integer,with outputs spaced by a fixed arbitrary distance at an edge of thesecond integrated circuit chip 604.

The first integrated circuit chip 602 and the second integrated circuitchip 604 can be aligned such that the outputs from the lasers 606-608 onthe first integrated circuit chip 602 align to the outputs from theresonators 610-612 on the second integrated circuit chip 604 (e.g.,waveguides evanescently coupled to each of the resonators 610-612). Asdescribed herein, each of the lasers 606-608 is aligned and coupled to acorresponding one of the resonators 610-612. Moreover, when aligned andwith the use of anti-reflection coatings and index matching epoxy, thefirst integrated circuit chip 602 and the second integrated circuit chip604 can be fixed in place such that the resonator cavities (e.g., theresonator 610-612) injection lock the lasers 606-608.

While many of the examples set forth herein describe the number oflasers 606-608 of the first integrated circuit chip 602 equaling thenumber of resonators 610-612 of the second integrated circuit chip 604,it is contemplated that a single resonator of the second integratedcircuit chip 604 can be optically coupled to more than one laser of thefirst integrated circuit chip 602. According to an example, the numberof lasers 606-608 can be larger than the number of resonators 610-612.Thus, the examples set forth herein to can be extended to such ascenario. Pursuant to an illustration, a single resonator (e.g., theresonator 610) of the second integrated circuit 604 can be configured toreceive light emitted by a first laser (e.g., the laser 606) of thefirst integrated circuit chip 602 and return feedback light to the firstlaser of the first integrated circuit chip 602, where the feedback lightreturned by the resonator can cause injection locking of the first laserto the resonator to control light emitted by the first laser. Followingthis illustration, the same resonator (e.g., the resonator 610) can alsobe configured to receive light emitted by a second laser (e.g., thelaser 608) of the first integrated circuit chip 602, where the feedbacklight returned by the resonator can cause injection locking of thesecond laser to the resonator to control the light emitted by the secondlaser.

When operated as part of an FMCW lidar sensor system, some of thechannels of the system 600 may be chirped at the same bandwidth/speed orcan be chirped at different bandwidths/speeds. Moreover, for differentwavelength lasers chirped at the same chirp slope, detected signals canbe processed to mitigate the impact of speckle from a target in theenvironment. Further, for lasers chirped at different rates or indifferent patterns, a common chipset can be used to cover differentlidar use cases with regards to range and resolution.

According to various embodiments, a multi-channel coupling of on-chipsource to electrooptic chip can be provided. Accordingly, multipleon-chip, narrow linewidth, low phase noise laser sources can beprovided. Moreover, on-chip multiplexing for a single scanner beam ofmultiple wavelengths can be outputted. Further, different chirp ratioscan be obtained for different FMCW sources utilizing a common system.The approaches herein provide for relatively low size, weight, power andcost as compared to conventional architectures.

Pursuant to an example, the multiple lasers 606-608 and resonators610-612 can be utilized to provide a multiple beam laser source toincrease pixel rate. For instance, in a lidar sensor system thatincludes the system 600, since multiple beams can be transmitted into anenvironment, an effective pixel rate within a scan time can be increased(relative to a lidar sensor system that transmits a single beam into theenvironment).

According to another example, optical frequencies of two or more of thelasers 606-608 can be offset from one another. Pursuant to anillustration, optical frequencies of each of the lasers 606-608 can beoffset from the other lasers 606-608 in the array. Pursuant to anotherexample, two or more of the lasers 606-608 can have substantiallysimilar optical frequencies (e.g., non-offset optical frequencies).According to an illustration, it is contemplated that a first laser canhave an optical frequency that is substantially similar to an opticalfrequency of a second laser, but differs from an optical frequency of athird laser.

Pursuant to an illustration, the laser 606 can have an optical frequencythat is offset relative to an optical frequency of the laser 608.Accordingly, the laser 606 and the laser 608 can operate with slightlydifferent wavelengths. Thus, the system 600 can provide an FMCW sourcethat outputs multiple beams of slightly different wavelengths, which canbe utilized to overcome problems such as speckle. For instance, adetermination can be made that a first optical frequency of the laser606 was deleteriously impacted, whereas a second optical frequency ofthe laser 608 was not similarly impacted. Thus, a return obtainedresponsive to the light emitted by the laser 608 operating at theoffset, second frequency can be used. According to another example,averaging of the returns can be used.

According to another example, two or more of the resonators 610-612 canbe modulated with different chirp patterns. Thus, different voltagewaveforms can be applied to electrodes adjacent to the resonatorsmodulated with the different patterns. For instance, chirp rates,slopes, and/or shapes of the voltage waveforms can be varied.Accordingly, different lasers 606-608 on the first integrated circuitchip 602 can be chirped at different rates, slopes, and/or functions tocover various use cases with regards to range, resolution, and detectionspeeds. For example, different chirp patterns can be used to tradeoffbetween short, midrange, and long-range detection of objects in anenvironment nearby the system 600.

Pursuant to another example, light emitted by two or more of the lasers606-608 can be phase shifted relative to each other. For instance, thelight emitted by the laser 606 (e.g., via a second path, transmitted toa lidar optical engine) can be phase shifted relative to the lightemitted by the laser 608 (e.g., via a differing second path, transmittedto a differing lidar optical engine). According to an example, phaseshifting of the outputs of the lasers 606-608 injection locked to thecorresponding resonators 610-612 can enable providing beam steering,which can create a phased array. Thus, the phase shifting of thechannels (e.g., by applying voltages to electrodes similar to theelectrodes 218-220 and/or the electrodes 402-404 described herein) canenable the system 600 to provide beam steering.

In accordance with another example, channels can be switched on and off.For instance, a first channel at a first operating frequency can be usedfor certain environmental conditions, whereas a second channel at asecond operating frequency can be used for differing environmentalconditions.

Moreover, according to an example, it is contemplated that outputs fromthe channels of the system 600 can be averaged. Such averaging canmitigate noise. Further, averaging of the outputs from the differentchannels to enhance a signal to noise ratio of a return may beadvantageous for automotive applications, where there oftentimes is notsufficient time to allow for averaging returns over time.

Now turning to FIG. 7 , illustrated is an exemplary embodiment of thesystem 600 that includes the first integrated circuit chip 602 and thesecond integrated circuit chip 604. Again, the first integrated circuitchip 602 includes the lasers 606. Further, the second integrated circuitchip 604 includes the resonators 610-612 and the mirrors 614-614.

Each of the lasers 606-608 can be optically coupled to a correspondinglidar optical engine 702-704. Each of the lidar optical engines 702-704can be substantially similar to the lidar optical engine 206 asdescribed above. Accordingly, the resonators 610-612 can be injectionlocked to the lasers 606-608, such that feedback light returned by theresonators 610-612 to the lasers 606-608 cause injection locking of thelasers 606-608 to the resonators 610-612 to control light emitted by thelasers 606-608 and inputted to the corresponding lidar optical engines702-704. Outputs from the lasers 606-608 in the second direction (e.g.away from the second integrated circuit chip 604) can be inputted intothe corresponding lidar optical engines 702-704. Each of the lidaroptical engines 702-704 can include a corresponding splitter, opticalamplifier, output, return, interferometer, balanced detector, and thelike.

As shown in FIG. 7 , light beams outputted from the lidar opticalengines 702-704 can be separately sent from the first integrated circuitchip 602. For instance, the light beams can be independently outputtedto separate beam steerers. Likewise, returned light beams provided tothe lidar optical engines 702-704 obtained responsive to the light beamsoutputted from the lidar optical engine 702-704 can be separate.

Now turning to FIG. 8 , illustrated is yet another exemplary embodimentof the system 600 that includes the first integrated circuit chip 602and the second integrated circuit chip 604. As depicted in FIG. 8 , thefirst integrated circuit chip 602 can further include a multiplexer 802and a demultiplexer 804. The multiplexer 802 can be configured tocombine light beams outputted from the lidar optical engines 702-704 ona single output channel for transmission into an environment. Thedemultiplexer 804 can be configured to separate returned light beamsreceived responsive to the transmission from the environment for thelidar optical engine 702-704 received on a single return channel.Accordingly, the light beams outputted by the lidar optical engine702-704 can be multiplexed to provide a single output channel anddemultiplexed on the return.

While not depicted in FIGS. 7-8 , it is contemplated that these examplescan be extended to a scenario where a single resonator is opticallycoupled to a plurality of lasers. For instance, the second integratedcircuit chip 604 can include one resonator, which can be opticallycoupled to the lasers 606-608. According to another example, a firstresonator of the second integrated circuit chip 604 can be opticallycoupled to more than one of the lasers 606-608, and a second resonatorof the second integrated circuit chip 604 can be optically coupled tomore than one of the lasers 606-608. It is also to be appreciated that aresonator of the second integrated circuit chip 604 can be opticallycoupled to more than one of the lasers 606-608, while a differentresonator of the second integrated circuit chip 604 can be opticallycoupled to one of the lasers 606-608.

Pursuant to another example, it is contemplated that a first integratedcircuit chip can include a laser and the second integrated circuit chipcan include a resonator, where the laser and the resonator are opticallycoupled. Following this example, an output of the laser injection lockedto the resonator can be split into multiple sources or channels. Forinstance, the multiple sources or channels outputted from the laser canbe inputted to multiple lidar optical engines. According to thisexample, each of the multiple lidar optical engines can have lightinputted thereto having substantially similar optical wavelengths(without an offset that may exist if differing lasers provide the lightto the multiple lidar optical engines). Outputs from the multiple lidaroptical engines can be separately outputted from the first integratedcircuit chip (similar to FIG. 7 ) or combined (similar to FIG. 8 ).

With reference to FIG. 9 , illustrated is an exemplary lidar sensorsystem 900. The lidar sensor system 900 can be a frequency modulatedcontinuous wave (FMCW) lidar sensor system; however, the claimed subjectmatter is not so limited. According to an example, an autonomous vehiclecan include the lidar sensor system 900. However, it is to beappreciated that the claimed subject matter is not so limited.

The lidar sensor system 900 includes a first integrated circuit chip 902(e.g., the first integrated circuit chip 106, the first integratedcircuit chip 602) and a second integrated circuit chip 904 (e.g., thesecond integrated circuit chip 108, the second integrated circuit chip604). The first integrated circuit chip 902 includes at least one laser906, and the second integrated circuit chip 904 includes at least oneresonator 908. The laser 906 is injection locked to the resonator 908.Moreover, the first integrated circuit chip 902 further includes atleast one lidar optical engine 910.

The resonator 908 can include electrodes to which a voltage can beapplied. Application of a voltage to the resonator 908 can change anoptical property of the electrooptic material of the resonator 908. Forinstance, application of a voltage can change an index of refraction ofthe electrooptic material of the resonator 908. The laser 906 isoptically injection locked to the resonator 908. Since the laser 906 isoptically injection locked to the resonator device 908, a voltageapplied to the resonator 908 can impart a frequency change on the laser906.

The lidar sensor system 900 further includes front end optics 912configured to transmit, into an environment of the lidar sensor system900, at least a portion of an injection locked light beam outputted viathe lidar optical engine 910 (e.g., generated from the light emitted bythe laser 906). According to various examples, the front end optics 912can include a scanner, which can direct an optical signal over a fieldof view in the environment. The front end optics 912 can also includeother optical elements, such as one or more lenses, an optical isolator,one or more waveguides, an optical amplifier, and so forth. Such opticalelements can enable generating the optical signal with desiredproperties such as collimation, divergence angle, linewidth, power, andthe like. Such optical elements may be assembled discretely, orintegrated on a chip, or in a combination of both. The front end optics912 can also be configured to receive a reflected optical signal fromthe environment. The reflected optical signal can correspond to at leasta part of the optical signal transmitted into the environment thatreflected off an object in the environment.

As described herein, the lidar optical engine 910 can mix the reflectedoptical signal received by the front end optics 912 with a localoscillator portion of the injection locked light beam generated by thelaser 906 injection locked to the resonator 908. Moreover, the lidarsensor system 900 can include processing circuitry 914, which can beconfigured to compute distance and velocity data of the object in theenvironment based on output of the lidar optical engine 910.

FIG. 10 illustrates an exemplary methodology related to injectionlocking a laser to a resonator. While the methodology is shown anddescribed as being a series of acts that are performed in a sequence, itis to be understood and appreciated that the methodology is not limitedby the order of the sequence. For example, some acts can occur in adifferent order than what is described herein. In addition, an act canoccur concurrently with another act. Further, in some instances, not allacts may be required to implement the methodology described herein.

FIG. 10 illustrates a methodology 1000 of injection locking a laser to aresonator. At 1002, light from a laser on a first integrated circuitchip can be emitted to a resonator on a second integrated circuit chipto generate an injection locked light beam. The first integrated circuitchip and the second integrated circuit chip are separate integratedcircuit chips. Moreover, the first integrated circuit chip and thesecond integrated circuit chip are optically coupled to each other. Theresonator can receive the light from the laser and return feedback lightto the laser. The feedback light can cause the laser to generate aninjection locked light beam. At 1004, the laser can output the injectionlocked light beam.

What has been described above includes examples of one or moreembodiments. It is, of course, not possible to describe everyconceivable modification and alteration of the above devices ormethodologies for purposes of describing the aforementioned aspects, butone of ordinary skill in the art can recognize that many furthermodifications and permutations of various aspects are possible.Accordingly, the described aspects are intended to embrace all suchalterations, modifications, and variations that fall within the scope ofthe appended claims. Furthermore, to the extent that the term “includes”is used in either the details description or the claims, such term isintended to be inclusive in a manner similar to the term “comprising” as“comprising” is interpreted when employed as a transitional word in aclaim.

What is claimed is:
 1. An integrated circuit chip, comprising: aresonator formed of an electrooptic material, the resonator configuredto receive light emitted by a laser and return feedback light to thelaser, wherein a separate integrated circuit chip comprises the laser,and wherein the feedback light causes injection locking of the laser ofthe separate integrated circuit chip to the resonator to control thelight emitted by the laser.
 2. The integrated circuit chip of claim 1,further comprising: a waveguide, wherein an end of the waveguide isconfigured to be optically coupled to the separate integrated circuitchip; and a mirror; wherein the resonator comprises: a first couplingregion evanescently coupled to the waveguide; and a second couplingregion evanescently coupled to the mirror.
 3. The integrated circuitchip of claim 2, wherein the mirror is tunable to control an amount oflight returned to the resonator.
 4. The integrated circuit chip of claim2, further comprising: electrodes adjacent to the waveguide such thatthe waveguide is between the electrodes, wherein a change in voltageapplied across the electrodes causes a corresponding phase shift of thefeedback light returned to the laser.
 5. The integrated circuit chip ofclaim 2, further comprising: a detector coupled to the waveguide, thedetector configured to detect alignment between the integrated circuitchip and the separate integrated circuit chip.
 6. The integrated circuitchip of claim 1, wherein the resonator is a closed-loop waveguide. 7.The integrated circuit chip of claim 1, wherein the resonator has awidth in a range from 1 micron to 3 microns.
 8. The integrated circuitchip of claim 1, further comprising: electrodes adjacent to theresonator such that the resonator is between the electrodes, wherein achange in voltage applied across the electrodes causes a correspondingchange in frequency of a waveguide mode of the resonator.
 9. Theintegrated circuit chip of claim 8, wherein the electrodes and theresonator are located in a common plane of the integrated circuit chiprelative to a top surface of a substrate of the integrated circuit chip.10. The integrated circuit chip of claim 8, wherein the electrodes andthe resonator are vertically stacked in the integrated circuit chiprelative to a top surface of a substrate of the integrated circuit chip.11. The integrated circuit chip of claim 1, wherein the resonator isfurther configured to receive light emitted by a differing laser andreturn feedback light to the differing laser, wherein the separateintegrated circuit chip further comprises the differing laser, andwherein the feedback light returned to the differing laser causesinjection locking of the differing laser of the separate integratedcircuit chip to the resonator to control the light emitted by thediffering laser.
 12. The integrated circuit chip of claim 1, furthercomprising: a second resonator formed of the electrooptic material, thesecond resonator configured to receive light emitted by a second laserand return feedback light to the second laser, wherein the separateintegrated circuit chip comprises the second laser, and wherein thefeedback light causes injection locking of the second laser of theseparate integrated circuit chip to the second resonator to control thelight emitted by the second laser.
 13. A system, comprising: a firstintegrated circuit chip, comprising: a first laser; and a second laser;and a second integrated circuit chip, the second integrated circuit chipand the first integrated circuit chip being separate integrated circuitchips, the second integrated circuit chip comprising: a resonator formedof an electrooptic material, the resonator configured to: receive lightemitted by the first laser of the first integrated circuit chip andreturn feedback light to the first laser of the first integrated circuitchip, wherein the feedback light returned by the resonator causesinjection locking of the first laser to the resonator to control thelight emitted by the first laser; and receive light emitted by thesecond laser of the first integrated circuit chip and return feedbacklight to the second laser of the first integrated circuit chip, whereinthe feedback light returned by the resonator causes injection locking ofthe second laser to the resonator to control the light emitted by thesecond laser.
 14. The system of claim 13, the first integrated circuitchip further comprises: a multiplexer configured to combine the lightemitted by the first laser and the light emitted by the second laser fortransmission into an environment; and a demultiplexer configured toseparate returned light received responsive to the transmission from theenvironment.
 15. The system of claim 13, wherein the light emitted bythe first laser is phase shifted relative to the light emitted by thesecond laser.
 16. The system of claim 13, wherein an optical frequencyof the first laser is offset from an optical frequency of the secondlaser.
 17. The system of claim 13, wherein the resonator is aclosed-loop waveguide.
 18. A method of injection locking a laser to aresonator, comprising: emitting light from the laser on a firstintegrated circuit chip to the resonator on a second integrated circuitchip, the first integrated circuit chip and the second integratedcircuit chip being separate integrated circuit chips, the firstintegrated circuit chip being optically coupled with the secondintegrated circuit chip; receiving feedback light from the resonator atthe laser, the feedback light causes injection locking of the laser tothe resonator; and transmitting injection locked light outputted by thelaser from the first integrated circuit chip into an environment. 19.The method of claim 18, further comprising: controlling a change involtage across electrodes to cause a phase shift of the feedback light.20. The method of claim 18, further comprising: controlling a change involtage across electrodes adjacent to the resonator to cause acorresponding change in frequency of a waveguide mode of the resonator.